1. Field of the Invention
This invention relates to a method of connecting semiconductor chips or dice to circuit substrates such as circuit boards.
2. Description of the Prior Art
In the prior art it is well known to connect semiconductor chips or dice to circuit substrates such as circuit boards, with adhesive. As noted in U.S. Pat. No. 5,012,969, methods are known for mounting a semiconductor up on a circuit substrate so that the semiconductor is placed face down on the circuit substrate in what is called a flip-chip arrangement. In such an arrangement, a solder bump may be formed on the electrode of the semiconductor die and this bump joined with a wiring electrode on the circuit substrate. In such methods, the electrodes of the semiconductor device and the electrodes of the circuit substrate are mechanically and electrically connected by the solder bumps. A problem in such a connection is that a thermal or mechanical stress acts on the semiconductor device or circuit substrate and the stress is entirely concentrated on the junctions of the solder bumps, possibly resulting in the breakage of some of the junctions and the lowering of the device reliability.
In accordance with one solution to this problem described in U.S. Pat. No. 4,749,120, an electrode is disposed on a semiconductor die and while positioning an electrode of a circuit substrate with the electrode of the die, an insulating resin is inserted between the front face of the semiconductor die and the circuit substrate and the insulating resin is stiffened or hardened while applying pressure to the back face of the semiconductor die. By making use of the contracting force of the insulating resin at the time of stiffening, the electrode of the semiconductor die is pressed against the electrode of the circuit substrate thereby obtaining an electrical connection.
As noted in U.S. Pat. No. 5,012,969, this solution causes a bending stress to be formed on the semiconductor die or circuit substrate, and the connection between the electrodes is partially impaired and it is difficult to obtain a favorable connection. Also, when the pressure is high, there is a risk of destroying the semiconductor die. This can be particularly a problem with fragile devices other than silicon such as GaAs.
Still further, since the insulating resin is formed on the entire from facing surface of the semiconductor die, when the semiconductor die or circuit substrate is heated and rises in temperature, the entire simulating resin tends to expand. When the force of expansion exceeds the contracting force, the electrode at the pressed part and the wiring electrode will separate from each other, and this often caused defective junctions. To overcome this noted problem of the prior art, the solution proposed in U.S. Pat. No. 5,9012,969 is to inject a light and heat-stiffening insulating resin about the periphery of the semiconductor die, at least in the gap between the die and the circuit substrate while applying pressure by means of a pressure tool to urge their respective electrodes into intimate contact. Afterwards a light source such as UV is placed proximate the periphery to stiffen the adhesive while further pressure is applied when irradiating.
A problem with this approach is that this process is time consuming in that light-sensitive adhesives require a light source to be moved about the periphery of the device nd the light-sensitive adhesives are relatively expansive.
It is, therefore, an object of the invention to overcome the problems associated with the prior art.